Heater element and portable heated container



Nov. 19, 1968 M. A. OTAVKA 3,412,234

HEATER ELEMENT AND PORTABLE HEATED CONTAINER Filed Oct. 25, 1966 @m/zwzmWm {far/er ///ar//q 5.

United States Patent 3,412,234 HEATER ELEMENT AND PORTABLE HEATEDCONTAINER Michael A. Otavka, 8016 Highland Ave.,

Downers Grove, Ill. 60515 Filed Oct. 25,1966, Ser. No. 589,353 Claims.(Cl. 219-406) This invention is in' the field of heated containers andis primarily concerned with a flexible resistive electrical heatingelement for use in a portable food preheater or warmer. 'Howeved, itshould be understood that this invention may be used as well in othercontainer applications which require heating.

A primary object of this invention is an inexpensive, easily fabricated,flexible, self-supportnig and adhering heater element.

' Another object is a heater element having multiple electricalconductors, each of which has a different resistance rating and isdesigned to operate with a specific voltage power source.

Another object is a sealed heating element having adhesive on at leastone side thereof.

Another object is a portable food preheater or warmer having uniformheating characteristics.

Another object is a rugged, easily fabricated, portable food preheateror warmer which may be operated from multiple voltage power sources suchas automobile, boat, truck, or household power.

Another object is a portable food preheater or warmer having fastcontainer warmup.

Another object is a container having uniform heating characteristics.

Another object is a heating element which economically providesflexibility in length and Wattage rating of such element.

Other objects will appear from time to time in the ensuing specificationand drawings in which:

FIGURE 1 is a perspective view in partial cross-section of an exemplaryform of the heated container of this invention;

FIGURE 2 is an enlarged view in partial cross-section, with portionsbroken away, showing an exemplary form of the heater element of thisinvention; and

FIGURE 3 is a wiring schematic of the exemplary heated container ofFIGURE 1.

Referring now to the drawings and particularly to FIGURE 1, an exemplaryform of the heated container of this invention has been shown asconsisting of a container having an opneing 12, with a closure member ordoor 14 swingably attached to said container by a hinge 16 so that saiddoor may be closed upon the opening 12 thereby forming a generallysealed enclosure. Although the container 10 has been depicted as beinggenerally square in cross-section and horizontal loading, it should beunderstood that the container may be otherwise configured, for example,it might be circular in cross-section and vertical loading.

The container 10 and door 14 are formed by an inner wall, such as at 18,and a spaced outer wall, such as at 20.

An elongated electrical heater element, shown generallyat 22, is wrappedaround the external surface of the inner wall 18 and attached andretained thereto by Ice adhesive existing on the side of said heaterelement which contacts the external surface of the inner wall.

A connetcor receptacle 24 and a temperature sensing regulating elementor thermostat 26 are electrically connected to the heater element 22 inaccordance with the wiring schematic of FIGURE 3. The thermostat 26 maybe either fixed or variable. If the thermostat is of the variable type,such thermostat would be mounted so as to be accessible, therebypermitting manual temperature selection.

Thermal insulation 28 is placed within the cavity formed by the innerwall 18 and spaced outer wall 20. The portable container may be providedwith feet 30 upon which the container will stand; a handle 32 for use intransporting such container; and a hasp 34 for use in fastening orretaining the closure member or door 14 in its closed position. A gasket36 may be provided around the periphery of the opening 12 so as to forma seal when the door is closed upon the opening 12.

Referring now to FIGURE 2, an exemplary form of the heater element ofthis invention is shown generally at 22. Such heater element comprises afirst elongated strip of electrical insualting material 38 havingadhesive on both sides thereof; resistive electrical conductors 40 and42 adhered to the tape strip 38 in spaced parallel relationship, withsuch conductors being generally parallel to and co-extensive with saidtape strip 38; and a second electrical insulating tape strip 44, havingadhesive on at least one side thereof, overlying and adhering to theconductors 40 and 42 and tape strip 38 being substantially co-extensivetherewith. A variety of materials may be utilized for the tape strips 38and 44. For example, the tape strips may be a silicone-bonded glasscloth backed mica matt, such as General Electric mica matt tape No.77581, which has been impregnated or coated with an adhesive; or, anadhesive faced silicone rubber tape. A tape material may also be used,such as above described, having an uncured epoxy resin binder which willflow under heat and pressure to form a bond between multiple layers ofsuch tape. Although the heater element of this invention provides goodthermal coupling between such element and the surface to be heatedbecause of the intimate contact of the heater element 22 with suchsurface, the thermal coupling may be increased by using a tape which hasbeen impregnated with silicone oil or other like impregnants. It shouldbe readily apparent that a plurality of tape materials having goodflexibility, strength, adhering qualities, voltage breakdown resistance,high temperature characteristics and good heat conductivity propertiesmay be used.

The heat generating resistive electrical conductors, such as 40 and 42,may be variously configured, for example, as shown in FIGURE 2, one suchconductor 40 may be generally rectangular in cross-sectional shape andone conductor 42 may be circular in cross-section.

In the exemplary embodiment of the heater element depicted in FIGURE 2and shown schematically wired to other container components in thewiring schematic of FIGURE 3, two resistive electrical conductors 40 and42 have been used, with one such conductor 40 having a high resistancerating while the second conductor 42 has a relatively low resistancerating so that the heater element 22 may be utilized with a plurality ofvoltage power supplies. For example, the high resistance conductor 40would be used with standard household 117 volt alternating current powerwhile the lower resistance conductor 42 might be used with a low voltagedirect current power source such as is available in an automobile, boat,or truck. It should be understood, however, that the heater element 22may be constructed with only one electrical conductor or more than twosuch electrical conductors respectively having either like or differentresistance ratings.

The exemplary heater elements 22 of FIGURE 2, as wired into theexemplary container of FIGURE 1, has been shown schematically in FIGURE3 wherein one end of each conductor 40 and 42 of said heater element 22is connected to a separate socket of the connector receptacle 24 and theother end of such conductors are electrically connected to each otherand to a third socket of the connector receptacle 24 through thethermostat 26. By so connecting the electrical conductors 40 and 42,selection of the particular electrical conductor to be connected to theavailable voltage power supply is facilitated. For example, to energizethe heated container from an automobile power source, an extension cordhaving at one end a connector adapted to plug into the automobilecigarette lighter and at the other end a male connector with pro trudingpins adapted to engage sockets 2, 3, and 4 as shown in the wiringschematic of FIGURE 3, of the receptacle 24 thereby energizing the lowresistance conductor 42; or, if the heated container is to be energizedusing standard 117 volt alternating current household power, anextension cord having at one end a standard two prong connector adaptedfor insertion into a standard household wall outlet and at the other enda male connector having protruding pins which are adapted to engagesockets 1, 3, and 4, of the connector receptacle 24, as shown in thewiring schematic of FIGURE 3, thereby energizing the high resistanceconductor 40. Accordingly, selection of the particular resistiveconductor to be used is accomplished by simply selecting the connectingextension cord. However, it should be understood that the heatedcontainer may be provided with other means of selecting the particularresistive conductor to be used such as a switch which connects,alternatively, either one resistive conductor or the other to one socketof a three socket connector receptacle.

Although the exemplary embodiment of the heater element has beendepicted and described as having two resistive conductors, either ofwhich may be connected in series, it should be understood that theheater element may contain only one electrical conductor or more thantwo electrical conductors and such conductors may be connectedsimultaneously in parallel. Further, although the exemplary heatedcontainer has been shown and described as having one continuous heaterelement 22 wrapped about the external surface of the inner wall 18, itshould be understood that a plurality of heater elements may be used andsuch elements may be connected in parallel or in series.

The heater element of this invention has the advantage of permittingeconomical fabrication of heated containers. Since the heater element isself-adhering or supporting, it may be applied to the surface to beheated by merely placing the element thereon. Because the element is inintimate contact with the surface to be heated, good heat transfer orsurface warm up results. Since the heater element is in tape formconsiderable flexibility in density of application result. For example,in the exemplary heated container of FIGURE 1, each coil of the heaterelement 22 may abut the preceding coil, so that upon completion ofwrapping, the external surface of the inner wall 18 is entirely coveredby the heater element; or, the heater element 22 may be wrapped aboutthe inner wall 18 so that spaces exist between successive heater elementcoils.

Another advantage of the heated container disclosed herein is uniformityin heating. Because the heater element 22 is wrapped along the entirelength and on four sides of the external surface of the inner wall 18,uniform heating results. Although the exemplary container of FIGURE 1has been depicted and described as having the heating element 22 wrappedabout only four walls thereof with no heating element on the inner Wallopposite the door 14, it should be understood that the heater elementmay be applied to such wall in, for example, a serpentine pattern.

While the preferred form and variation of the invention have beendescribed, it should be understood that suitable other additions,alterations, and variations may be made without departing from theinventions fundamental theme.

I claim:

1. A container having an inner and outer wall, at least one heatingelement attached to the external surface of said inner wall, insulatingmaterial between said heating elements and the internal surface of saidouter wall, said heating elements including a first strip of electricalinsulating tape adhering to the external surface of said inner wall, atleast one resistive electrical conductor member adhering to, parallelingand co-extensive with the external surface of said first tape strip, asecond strip of electrical insulating tape adhering to, overlying andco-extensive with said first tape strip and said resistive electricalconductor, said tape strips together enclosing said conductortherebetween said heating element containing a first high resistanceelectrical conductor and a second low resistance electrical conductoradhered in spaced parallel relationship to said external surface of saidfirst tape strip so that said container may be heated using more thanone voltage power source.

2. The structure of claim 1 further characterized in that said containercontains connective selection means whereby either one of saidelectrical conductors may be selected and connected to an electricalpower source.

3. The structure of claim 1 further characterized in that said containercontains a temperature sensing regulating element connected to saidconductor which substantially maintains the temperature within saidcontainer at a preselected temperature.

4. A container including a continuous sidewall, a closure wall swingablyjoining one edge of said sidewall, said walls being formed of spacedinner and outer metal sheets, insulation material between said sheetsand an elongated heating element wrapped about and adhering to theexternal surface of the inner metal sheet of said sidewall, said heaterelement comprising a first elongated strip of electrical insulatingtape, at least one resistive electrical conductor adhered to the saidfirst tape strip and a second elongated electrical insulating tape stripadhered to and overlying said first tape strip and said conductor, saidconductor and said first and second tape strips being substantiallyco-extensive in length, and a temperature sensing regulating elementsecured to said conductor and penetrating said outer sheet, said heaterelement comprising a plurality of electrical conductors, each suchconductor having a different resistance rating, said conduc tors adheredto said first side of said first tape strip in spaced parallelrelationship, with said container including connective and selectionmeans whereby any of said elec* trical conductors may be selected andconnected to an electrical power source.

5. A portable heater including: a continuous sidewall; said sidewallforming a container having an opening; a closure wall swingably attachedto said container adjacent a sidewall edge forming said opening; meansfor retaining said closure wall in a position closing said containeropening; at least one handle attached to said continuous side wall; saidwalls being formed of spaced inner and outer sheets; insulation materialbetween said sheets and an elongated heating element wrapped about andadhering to the external surface of said inner sheet; said heatingelement comprising a first elongated strip of electrical insulatingtape, a plurality of electrical conductors, each such conductor having adifferent resistance rating; said conductors adhered in spaced parallelrelationship to one surface of said first tape strip, and a second stripof electrical insulating tape adhered to and overlying said first stripand said conductors, said conductors and said first and second tapestrips being substantially co-extensive in length; connector andselection means for optionally electrically connecting one of saidresistive electrical conductors to multiple external voltage powersources; and a temperature sensing regulating element secured to saidconductors and penetrating said outer sheet for use in substantiallymaintaining a preselected temperature Within said container.

6 References Cited UNITED STATES PATENTS 822,270 6/1906 I-Iaagn 219-406X 5 2,505,117 4/1950 Hoffmann 219-407 X 3,004,130 10/1961 Miller219--386 X 3,019,325 1/1962 Clouse 219546 X 3,029,303 4/1962 Severino174-117 X 10 BERNARD A. GILHEANY, Primary Examiner.

H. B. GILSON, Assistant Examiner.

1. A CONTAINER HAVING AN INNER AND OUTER WALL, AT LEAST ONE HEATINGELEMENT ATTACHED TO THE EXTERNAL SURFACE OF SAID INNER WALL, INSULATINGMATERIAL BETWEEN SAID HEATING ELEMENTS AND THE INTERNAL SURFACE OF SAIDOUTER WALL, SAID HEATING ELEMENTS INCLUDING A FIRST STRIP OF ELECTRICALINSULATING TAPE ADHERING TO THE EXTERNAL SURFACE OF SAID INNER WALL, ATLEAST ONE RESISTIVE ELECTRICAL CONDUCTOR MEMBER ADHERING TO, PARALLELINGAND CO-EXTENSIVE WITH THE EXTERNAL SURFACE OF SAID FIRST TAPE STRIP, ASECOND STRIP OF ELECTRICAL INSULATING TAPE ADHERING TO, OVERLYING ANDCO-EXTENSIVE WITH SAID FIRST TAPE STRIP AND SAID RESISTIVE ELECTRICALCONDUCTOR, SAID TAPE STRIPS TOGETHER ENCLOSING SAID CONDUCTORTHEREBETWEEN, SAID HEATING ELEMENT CONTAINING A FIRST HIGH RESISTANCEELECTRICAL CONDUCTOR AND A SECOND LOW RESISTANCE ELECTRICAL CONDUCTORADHERED IN SPACED PARALLEL RELATIONSHIP TO SAID EXTERNAL SURFACE OF SAIDFIRST TAPE STRIP SO THAT SAID CONTAINER MAY BE HEATED USING MORE THANONE VOLTAGE POWER SOURCE.